tag: add a boolean tag

tag.c

@@ -7,6 +7,7 @@ struct private {
     char *name;
     union {
         long value_as_int;
+        bool value_as_bool;
         double value_as_float;
         char *value_as_string;
     };
@@ -46,6 +47,13 @@ value_int(const struct tag *tag)
     return as_string;
 }
 
+static const char *
+value_bool(const struct tag *tag)
+{
+    const struct private *priv = tag->private;
+    return priv->value_as_bool ? "true" : "false";
+}
+
 static const char *
 value_float(const struct tag *tag)
 {
@@ -78,6 +86,21 @@ tag_new_int(const char *name, long value)
     return tag;
 }
 
+struct tag *
+tag_new_bool(const char *name, bool value)
+{
+    struct private *priv = malloc(sizeof(*priv));
+    priv->name = strdup(name);
+    priv->value_as_int = value;
+
+    struct tag *tag = malloc(sizeof(*tag));
+    tag->private = priv;
+    tag->destroy = &destroy_int_and_float;
+    tag->name = &tag_name;
+    tag->value = &value_bool;
+    return tag;
+}
+
 struct tag *
 tag_new_float(const char *name, double value)
 {

tag.h

@@ -2,6 +2,8 @@
 
 #include <stddef.h>
 
+#include <stdbool.h>
+
 struct tag {
     void *private;
 
@@ -16,6 +18,7 @@ struct tag_set {
 };
 
 struct tag *tag_new_int(const char *name, long value);
+struct tag *tag_new_bool(const char *name, bool value);
 struct tag *tag_new_float(const char *name, double value);
 struct tag *tag_new_string(const char *name, const char *value);